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Message-Id: <20200819133630.527243-3-alexandru.elisei@arm.com>
Date: Wed, 19 Aug 2020 14:36:30 +0100
From: Alexandru Elisei <alexandru.elisei@....com>
To: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
kvmarm@...ts.cs.columbia.edu
Cc: jason@...edaemon.net, maz@...nel.org, catalin.marinas@....com,
tglx@...utronix.de, will@...nel.org, yuzenghui@...wei.com
Subject: [PATCH v2 2/2] irqchip/gic-v3: Support pseudo-NMIs when SCR_EL3.FIQ == 0
The GIC's internal view of the priority mask register and the assigned
interrupt priorities are based on whether GIC security is enabled and
whether firmware routes Group 0 interrupts to EL3. At the moment, we
support priority masking when ICC_PMR_EL1 and interrupt priorities are
either both modified by the GIC, or both left unchanged.
Trusted Firmware-A's default interrupt routing model allows Group 0
interrupts to be delivered to the non-secure world (SCR_EL3.FIQ == 0).
Unfortunately, this is precisely the case that the GIC driver doesn't
support: ICC_PMR_EL1 remains unchanged, but the GIC's view of interrupt
priorities is different from the software programmed values.
Support pseudo-NMIs when SCR_EL3.FIQ == 0 by using a different value to
mask regular interrupts. All the other values remain the same.
Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
---
arch/arm64/include/asm/arch_gicv3.h | 8 ++++-
arch/arm64/include/asm/daifflags.h | 4 +--
arch/arm64/include/asm/irqflags.h | 18 ++++++----
arch/arm64/include/asm/ptrace.h | 12 +++++++
arch/arm64/kernel/entry.S | 2 +-
arch/arm64/kernel/image-vars.h | 2 ++
arch/arm64/kvm/hyp/nvhe/switch.c | 2 +-
drivers/irqchip/irq-gic-v3.c | 52 ++++++++++++++++++++++-------
8 files changed, 77 insertions(+), 23 deletions(-)
diff --git a/arch/arm64/include/asm/arch_gicv3.h b/arch/arm64/include/asm/arch_gicv3.h
index 6647ae4f0231..908152e8659b 100644
--- a/arch/arm64/include/asm/arch_gicv3.h
+++ b/arch/arm64/include/asm/arch_gicv3.h
@@ -162,7 +162,13 @@ static inline void gic_pmr_mask_irqs(void)
* are applied to IRQ priorities
*/
BUILD_BUG_ON((0x80 | (GICD_INT_DEF_PRI >> 1)) >= GIC_PRIO_IRQON);
- gic_write_pmr(GIC_PRIO_IRQOFF);
+ /*
+ * Same situation as above, but now we make sure that we can mask
+ * regular interrupts.
+ */
+ BUILD_BUG_ON((0x80 | (GICD_INT_DEF_PRI >> 1)) < (GIC_PRIO_IRQOFF_NS |
+ GIC_PRIO_PSR_I_SET));
+ gic_write_pmr(gic_prio_irqoff());
}
static inline void gic_arch_enable_irqs(void)
diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
index ec213b4a1650..3efa240a6c48 100644
--- a/arch/arm64/include/asm/daifflags.h
+++ b/arch/arm64/include/asm/daifflags.h
@@ -22,7 +22,7 @@
static inline void local_daif_mask(void)
{
WARN_ON(system_has_prio_mask_debugging() &&
- (read_sysreg_s(SYS_ICC_PMR_EL1) == (GIC_PRIO_IRQOFF |
+ (read_sysreg_s(SYS_ICC_PMR_EL1) == (gic_prio_irqoff() |
GIC_PRIO_PSR_I_SET)));
asm volatile(
@@ -87,7 +87,7 @@ static inline void local_daif_restore(unsigned long flags)
* asynchronous errors, we can take NMIs
*/
flags &= ~PSR_I_BIT;
- pmr = GIC_PRIO_IRQOFF;
+ pmr = gic_prio_irqoff();
} else {
pmr = GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET;
}
diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
index aa4b6521ef14..af353c78d5f8 100644
--- a/arch/arm64/include/asm/irqflags.h
+++ b/arch/arm64/include/asm/irqflags.h
@@ -28,10 +28,13 @@
*/
static inline void arch_local_irq_enable(void)
{
+ u64 pmr_irqon = GIC_PRIO_IRQON;
+
if (system_has_prio_mask_debugging()) {
- u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
+ u64 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
+ u64 pmr_irqoff = gic_prio_irqoff();
- WARN_ON_ONCE(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
+ WARN_ON_ONCE(pmr != pmr_irqon && pmr != pmr_irqoff);
}
asm volatile(ALTERNATIVE(
@@ -39,7 +42,7 @@ static inline void arch_local_irq_enable(void)
__msr_s(SYS_ICC_PMR_EL1, "%0"),
ARM64_HAS_IRQ_PRIO_MASKING)
:
- : "r" ((unsigned long) GIC_PRIO_IRQON)
+ : "r" (pmr_irqon)
: "memory");
pmr_sync();
@@ -47,10 +50,13 @@ static inline void arch_local_irq_enable(void)
static inline void arch_local_irq_disable(void)
{
+ u64 pmr_irqoff = gic_prio_irqoff();
+
if (system_has_prio_mask_debugging()) {
- u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
+ u64 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
+ u64 pmr_irqon = GIC_PRIO_IRQON;
- WARN_ON_ONCE(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
+ WARN_ON_ONCE(pmr != pmr_irqon && pmr != pmr_irqoff);
}
asm volatile(ALTERNATIVE(
@@ -58,7 +64,7 @@ static inline void arch_local_irq_disable(void)
__msr_s(SYS_ICC_PMR_EL1, "%0"),
ARM64_HAS_IRQ_PRIO_MASKING)
:
- : "r" ((unsigned long) GIC_PRIO_IRQOFF)
+ : "r" (pmr_irqoff)
: "memory");
}
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index 966ed30ed5f7..a19cd6ff4d1b 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -32,6 +32,7 @@
*/
#define GIC_PRIO_IRQON 0xe0
#define GIC_PRIO_IRQOFF (GIC_PRIO_IRQON & ~0x80)
+#define GIC_PRIO_IRQOFF_NS 0xa0
#define GIC_PRIO_PSR_I_SET (1 << 4)
/* Additional SPSR bits not exposed in the UABI */
@@ -129,6 +130,17 @@
#define compat_sp_fiq regs[29]
#define compat_lr_fiq regs[30]
+#define gic_prio_irqoff() \
+ ({ \
+ extern struct static_key_false gic_nonsecure_priorities;\
+ u8 __prio = GIC_PRIO_IRQOFF; \
+ \
+ if (static_branch_unlikely(&gic_nonsecure_priorities)) \
+ __prio = GIC_PRIO_IRQOFF_NS; \
+ \
+ __prio; \
+ })
+
static inline unsigned long compat_psr_to_pstate(const unsigned long psr)
{
unsigned long pstate;
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 2646178c8329..e4fa944dbf1d 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -653,7 +653,7 @@ alternative_else_nop_endif
#ifdef CONFIG_ARM64_PSEUDO_NMI
/*
* When using IRQ priority masking, we can get spurious interrupts while
- * PMR is set to GIC_PRIO_IRQOFF. An NMI might also have occurred in a
+ * PMR is set to mask interrupts. An NMI might also have occurred in a
* section with interrupts disabled. Skip tracing in those cases.
*/
test_irqs_unmasked res=x0, pmr=x20
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index 9e897c500237..c4476a99dee8 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -101,6 +101,8 @@ KVM_NVHE_ALIAS(vgic_v3_cpuif_trap);
/* Static key checked in pmr_sync(). */
#ifdef CONFIG_ARM64_PSEUDO_NMI
KVM_NVHE_ALIAS(gic_pmr_sync);
+/* Static key checked in gic_prio_irqoff(). */
+KVM_NVHE_ALIAS(gic_nonsecure_priorities);
#endif
#endif /* CONFIG_KVM */
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 341be2f2f312..729a3a59ad6a 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -237,7 +237,7 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
/* Returning to host will clear PSR.I, remask PMR if needed */
if (system_uses_irq_prio_masking())
- gic_write_pmr(GIC_PRIO_IRQOFF);
+ gic_write_pmr(gic_prio_irqoff());
return exit_code;
}
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index ce8944ae1b84..19e52c025c59 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -75,16 +75,14 @@ static DEFINE_STATIC_KEY_TRUE(supports_deactivate_key);
*
* If SCR_EL3.FIQ == 1, the values writen to/read from PMR and RPR at non-secure
* EL1 are subject to a similar operation thus matching the priorities presented
- * from the (re)distributor when security is enabled.
+ * from the (re)distributor when security is enabled. When SCR_EL3.FIQ == 0,
+ * these values are unchanched by the GIC.
*
* see GICv3/GICv4 Architecture Specification (IHI0069D):
* - section 4.8.1 Non-secure accesses to register fields for Secure interrupt
* priorities.
* - Figure 4-7 Secure read of the priority field for a Non-secure Group 1
* interrupt.
- *
- * For now, we only support pseudo-NMIs if we have non-secure view of
- * priorities.
*/
static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);
@@ -97,6 +95,9 @@ static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);
DEFINE_STATIC_KEY_FALSE(gic_pmr_sync);
EXPORT_SYMBOL(gic_pmr_sync);
+DEFINE_STATIC_KEY_FALSE(gic_nonsecure_priorities);
+EXPORT_SYMBOL(gic_nonsecure_priorities);
+
/* ppi_nmi_refs[n] == number of cpus having ppi[n + 16] set as NMI */
static refcount_t *ppi_nmi_refs;
@@ -932,14 +933,16 @@ static void gic_cpu_sys_reg_init(void)
/* Set priority mask register */
if (!gic_prio_masking_enabled()) {
write_gicreg(DEFAULT_PMR_VALUE, ICC_PMR_EL1);
- } else {
+ } else if (gic_supports_nmi()) {
/*
* Mismatch configuration with boot CPU, the system is likely
* to die as interrupt masking will not work properly on all
* CPUs
*/
- WARN_ON(gic_supports_nmi() && group0 &&
- !gic_dist_security_disabled());
+ if (static_branch_unlikely(&gic_nonsecure_priorities))
+ WARN_ON(!group0 || gic_dist_security_disabled());
+ else
+ WARN_ON(group0 && !gic_dist_security_disabled());
}
/*
@@ -1544,11 +1547,6 @@ static void gic_enable_nmi_support(void)
if (!gic_prio_masking_enabled())
return;
- if (gic_has_group0() && !gic_dist_security_disabled()) {
- pr_warn("SCR_EL3.FIQ is cleared, cannot enable use of pseudo-NMIs\n");
- return;
- }
-
ppi_nmi_refs = kcalloc(gic_data.ppi_nr, sizeof(*ppi_nmi_refs), GFP_KERNEL);
if (!ppi_nmi_refs)
return;
@@ -1567,6 +1565,36 @@ static void gic_enable_nmi_support(void)
pr_info("Pseudo-NMIs enabled using %s ICC_PMR_EL1 synchronisation\n",
static_branch_unlikely(&gic_pmr_sync) ? "forced" : "relaxed");
+ /*
+ * How priority values are used by the GIC depends on two things:
+ * the security state of the GIC (controlled by the GICD_CTRL.DS bit)
+ * and if Group 0 interrupts can be delivered to Linux in the non-secure
+ * world as FIQs (controlled by the SCR_EL3.FIQ bit). These affect the
+ * the ICC_PMR_EL1 register and the priority that software assigns to
+ * interrupts:
+ *
+ * GICD_CTRL.DS | SCR_EL3.FIQ | ICC_PMR_EL1 | Group 1 priority
+ * -----------------------------------------------------------
+ * 1 | - | unchanged | unchanged
+ * -----------------------------------------------------------
+ * 0 | 1 | non-secure | non-secure
+ * -----------------------------------------------------------
+ * 0 | 0 | unchanged | non-secure
+ *
+ * where non-secure means that the value is right-shifted by one and the
+ * MSB bit set, to make it fit in the non-secure priority range.
+ *
+ * In the first two cases, where ICC_PMR_EL1 and the interrupt priority
+ * are both either modified, or unchanged, we can use the same set of
+ * priorities.
+ *
+ * In the last case, where only the interrupt priorities are modified to
+ * be in the non-secure range, we use a different PMR value to mask IRQs
+ * and the rest of the values that we use remain unchanged.
+ */
+ if (gic_has_group0() && !gic_dist_security_disabled())
+ static_branch_enable(&gic_nonsecure_priorities);
+
static_branch_enable(&supports_pseudo_nmis);
if (static_branch_likely(&supports_deactivate_key))
--
2.28.0
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